Oil damper system

ABSTRACT

The oil shock absorber system includes a piston and cylinder arrangement for driving oil from the cylinder to a reservoir. The reservoir includes a reserve chamber and a chamber intermediate the cylinder and the reserve chamber. A flow path including three different orifices communicate between the intermediate and reserve chambers, with two orifices having adjustable non-return valves. One valve constitutes an adjustable hydraulic brake evacuating oil from the intermediate chamber into the reserve chamber only when the cylinder pressure exceeds a predetermined pressure. The second valve is adjustable for a range of piston displacement speeds that lies between a first low speed and hydraulic brake speeds.

BACKGROUND OF THE INVENTION

This invention relates to an oil shock absorber system for motorcyclesor automobiles and in particular for vehicles that are used either forracing or for all-terrain driving.

An oil shock absorber that comprises a mobile piston in a cylinderwhich, during its compression travel, displaces the oil that iscontained in a chamber toward, on the one hand, a reservoir and, on theother, a second chamber that is located on the other side of the piston,is known from U.S. patent application Ser. No. 4,958,706. The path ofthe oil toward the second chamber that is located on the other side ofthe piston runs through valves for adjusting the resiliencecharacteristics of the shock absorber. The pressure of the oil that isdriven into the reservoir is balanced by a pocket that holds apressurized gas and that plays, as it were, a role equivalent to that ofthe spring in the spring shock absorbers of the prior art. Access to thechamber of the reservoir is limited by, on the one hand, a system thatcan be adjusted by a screw for adjusting the compression rate, and, onthe other, a valve for protection against excessive pressure that is setto withstand a maximum pressure of about 140 Kg/cm² (2000 psi).

A shock absorber system that comprises a cylinder in which a mobilepiston delimits two working volumes is also known from InternationalPatent Application WO 94 12360. Each volume is connected, via a pipe, toan intermediate volume. The two intermediate volumes each communicate bythree orifices with the same control chamber. The three orificesrespectively comprise a valve for regulating the flow of oil from theintermediate volume to the control chamber, an adjustable nonreturnvalve that constitutes a hydraulic brake, and a valve that allows apermanent passage from the control chamber to the intermediate volume.This relatively complex system makes it possible to adjust thecharacteristics of compression and of stress relief of a shock absorberindependently, but it does not allow optimum adjustment of the shockabsorber for operations in a range of displacement speeds of the pistonthat lies between low speeds and hydraulic brake speeds.

This invention relates to an oil reservoir that can be used with such ashock absorber or with other simpler or more complex shock absorbertypes. Actually, it has been noted that in these shock absorber systems,an elastic element that generally consists of a rubber ring is alwaysprovided on the shock absorber, between, on the one hand, ring (11) thatis placed at the end of rod (10) of the piston that is adjacent toattachment ring (12) on the frame of the vehicle and, on the other hand,lower outside surface (151) of cylindrical body (15) that constitutesthe compression chamber which forms the shock absorber stop that isencountered under extreme operating conditions. Actually, since theshock absorber is protected against excessive pressure, the valve of thereservoir is likely to open when the vehicle falls back after a majorbounce, and, in this case, the only protection for the shock absorber isthe elastic bearing that is located between cylinder (15) and ring (11).

The elastic bearing has the drawback of generating uncontrollablebouncing phenomena for the driver which sometimes bring the vehicle totip violently to the front.

SUMMARY OF THE INVENTION

A first object of the invention is to propose a shock absorber systemthat makes it possible to eliminate these drawbacks and to improve theresponse characteristics of the shock absorber during compression phaseswhile retaining the advantages and characteristics of oil shockabsorbers.

This object is achieved by the fact that the oil shock absorber systemthat consists of a piston that is mounted at the end of a movable rodthat moves in a cylindrical hollow body by driving the oil that isbetween the piston and the bottom of the hollow body of the shockabsorber toward a deformable reserve chamber, to the outside of which apressurized gas is applied, whereby the oil that is evacuated to thereserve chamber via at least two different orifices, depending on thedisplacement speeds of the piston, is characterized in that the path ofthe oil runs through an intermediate chamber of a given volume and theorifices are located between the reserve chamber and the intermediatechamber, whereby at least one of the orifices or the first orifice isblocked by an adjustable nonreturn valve that constitutes an adjustablehydraulic brake so as to allow the oil to evacuate only when thepressure that is exerted by the piston on the oil is such that itexceeds the vehicle's most extreme anticipated operating conditions, andin that a second adjustable nonreturn valve blocks a second orifice thatis located between the intermediate chamber and the reserve chamber,whereby the second adjustable nonreturn valve is adjusted for a range ofdisplacement speeds of the piston that lies between low speeds andhydraulic brake speeds.

According to another particular feature, a third orifice that isprovided with an adjustable constriction makes it possible at low speedsto evacuate oil from the intermediate chamber to the reserve chamber.

According to another particular feature, the first and second valvescomprise a screw element that is extended by a notched rod uniformlyover a given height of its periphery and that supports on the end of therod means for attaching a holding cap, whereby a sealing washer (354)and an elastic means are held between the holding cap and the notchedpart, and the elastic means presses the sealing washer with a specificforce on the seat of the respective orifice that is associated with thevalve.

According to another particular feature, the notched part works with aball on which elastic means act to constitute an adjusting catch.

According to another particular feature, the intermediate chamberconsists of an annular groove that is formed in a cylindrical ring thatis intended to close the open end of the reservoir, whereby thecylindrical ring is provided with holes that run through the ring andthe annular groove, whereby the holes comprise, on the outside of thereservoir, threading for the screw element and means that make itpossible to ensure sealing between the screw body and the hole.

According to another particular feature, the elastic means that pressthe sealing washer against the seat of the hole consist of a stack ofseveral beleville washers that are mounted two by two opposite oneanother.

According to another particular feature, the elastic means for thehigh-speed screw consist of a stack of beleville washers with athickness of between 0.20 mm and 0.45 mm.

According to another particular feature, the elastic means for thehydraulic stop screw consist of a stack of beleville washers with athickness of between 0.45 mm and 1 mm, with a greater thickness for thewashers of the stop screw than that of the washers of the high-speedscrew.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Other particular features and advantages of this invention will becomeclearer from reading the description below, which is given withreference to the accompanying drawings, where:

FIG. 1 depicts a diagrammatic view of the principle of the invention;

FIG. 2A depicts a detail view and a partial cutaway view of adjustablevalves;

FIG. 2B depicts a top view of the notched portion of the screw;

FIG. 2C depicts a bottom view of the closing ring of the reservoir;

FIG. 2D depicts a side view of the ring;

FIG. 2E depicts a cutaway view along the line that runs through the twoaxes of symmetry of the two adjustable valves;

FIG. 3 depicts the curve that expresses the force responsecharacteristics depending on the compression speed.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described with FIGS. 1 to 3.

The shock absorber system consists of a hollow cylinder (15) in whichmoves a piston (13) that is located at the end of a rod (10) whose otherend has an eyelet (12) for mounting on the vehicle and, close to theeyelet, a thrust washer (11). The end of cylinder (15) that is oppositeeyelet (12) also comprises an eyelet (14) for mounting on the vehicle.When the vehicle moves, the rod will be acted on by compression orextension and, during the compression phases, the fluid that is betweenpiston (13) and the bottom of chamber (15) that is close to eyelet (14)of cylinder (15) will be driven via pipe (2) toward a reservoir (3). Thereservoir (3) comprises a reserve chamber (4) that is delimited by acylindrical piston (31) that moves freely in the reservoir under theaction of the pressures of fluid (4) and a gas (5) that is introducedinto the zone that is between the other face of piston (31) and thebottom of the reservoir. The fluid is introduced in a known way via afilling nonreturn valve (6). Sealing between the gas and the fluid isensured by an annular seal (310) that is placed in a peripheral grooveof piston (31). Pipe (2) is connected to the reservoir by a joiningpiece (33), one end of which empties into an intermediate chamber (321)that is formed in a ring (32). The intermediate chamber (321) leads intooil reserve chamber (4) via three orifices (325, 322, 326), two of whichare blocked by a nonreturn valve and the third (322), which is providedwith an adjustable constriction that can be open to a greater or lesserextent. For example, a float-needle screw (34) is placed in the threadedhole of ring (32). Float needle (34) comes to seal more or less taperedorifice (322). The float needle screw (34) comprises a seal (9) betweenannular chamber (321) and the outside part of ring (32). The floatneedle screw can be replaced by any other equivalent means such as, forexample, a calibrated slot.

Communication between intermediate chamber (321) and reserve chamber (4)is prevented by at least one nonreturn valve, and, in the variant thatis depicted in FIG. 1, by two adjustable nonreturn valves (35, 36), aswill be seen below. Each of the nonreturn valves is made in a way thatis identical to that depicted in FIG. 2A. The valve is formed by awasher (354) that presses on the seat that is delimited by cylindricalhole (3252) which has a diameter that is larger than hole (3251) forforming the seat of the valve. Hole (3251) comprises a threaded part atits end that faces the seat. The hole (3251) empties to the outside ofring (32) via a hole with a larger diameter, forming a shoulder (3253)with the threaded part. Likewise, valve (36) will comprise a ring (364),whereby hole (3262) forms the seat with threaded hole (3261) andshoulder (3263). Each sealing washer (354, 364) is mounted on a rod(3512, or 3612) that comprises at its end a hole in which runs a pin(358, or 368) that makes the rod integral with a cap (359, or 369) whosesection is substantially U-shaped and comprises, in the central part ofthe U, holes (3590) for the passage of the oil. Beleville washers (355a, 355 b, 356 a, 356 b) that are mounted two by two opposite one another(365 a, 365 b; 366 a, 366 b) are placed under cap (359, 369). For valve(36), there is also a given number of beleville washers that are mountedtwo by two opposite one another to constitute an elastic means thatpresses with a given force sealing washer (354, or 364) against, on theone hand, the seat of the hole and, on the other, a notched ring (353,or 363) that is integral with respective rod (3512, 3612) of each screwof each valve (35, 36). Each notched ring (353, 363) comprises,distributed uniformly over its periphery, slots (3531, 3631) thatconstitute housings for a ball (8 a, or 8 b) which is acted on by aspring (7 a, or 7 b) in such a way that ball (8 a, or 8 b) lodges inrespective slot (3531, 3631) of the notched ring that faces it. Thenotched ring is made integral with the rod on which it is mounted bysuitable means, such as, for example, brazing. The rod is extended fromthe side of the head of screw (351, or 361) by a threaded part (3513, or3613), and the screw head comprises a widening in diameter in which isformed a groove that makes it possible to install a seal (352, or 362).Each of the screw beads comprises a groove (3511) for first screw (35)and a cross groove (3611) for second screw (36), as can be seen in FIG.2C. With a tool, these grooves make it possible to unscrew notch bynotch each of the screws that constitute an adjusting valve, which hasthe effect of compressing the beleville washers between washer (354 or364) and respective cap (359, 369). This makes it possible to determinethe compression force beyond which the valve will open. Sealing betweenring (32) and the cylindrical wall of reservoir (30) is achieved by twotoric seals (358, 357) that are each placed in a peripheral groove(3258, 3257) that is formed on both sides of the annular groove thatconstitutes intermediate chamber (321).

As can be seen in FIG. 3, the diagram that depicts the variation of thecharacteristics of the shock absorber as a function of compression speedand compression force will vary based on the adjustment that is made toeach of the screws. Then, when float-needle screw (34) that constitutesthe so-called low-speed screw is adjusted, point A of the curve moves upor down, as indicated by arrows (34) of FIG. 3. The more orifice (322)is constricted by the float needle of the screw, the faster this orificewill become saturated, and flow will have to take place via thehigh-speed valve. Consequently, tightening screw (34) causes curve (340)to move in the direction of arrow S. When orifice (322) saturates, thepressure in the intermediate chamber increases and reaches theresistance force that is constituted by beleville washers (355, 356) offirst valve (35), which detaches sealing washer (354) from its seat,thus making it possible for the fluid to flow from intermediate chamber(321) toward reserve chamber (4) via the annular space that is availablebetween notched crown (353) and hole (3251). When the displacement speedof the piston or the pressure of the fluid increases greatly, firstadjustable valve (35) will saturate, and the pressure will continue toincrease by pushing against second valve (36) that constitutes thehydraulic stop. The second valve (36) comprises beleville washers with alarger thickness, and screw (361) is adjusted in such a way that washer(364) rests on its seat until the compression speed and compressionforce have reached point C of curve (3640). In the working zone, theshock absorber therefore retains a response characteristic that is afunction of pressure and speed, which thus constitutes a hydraulicbrake. When pressure and speed exceed point C of the curve, valve (364)opens, and the oil flows toward the reservoir via the valve. Thethickness of the washers can be adapted based on the valve and theapplication. Also on motorcycle or 4×4 automobile shock absorbers, it ispossible to mount washers with a thickness of 0.45 mm for the high-speedscrew and 0.65 mm for the stop screw or hydraulic brake. In otherapplications such as an all-terrain vehicle or VTC, thicknesses of, forexample, 0.20 mm will be used for the high-speed screw and of 0.45 mmfor the stop screw or hydraulic brake. These thicknesses are determinedby one skilled in the art based on the loads that are tolerated by eachshock absorber and the type of use and the desired compression responsecurve.

The compression force curve that is based on the compression speed orthe displacement of the cylinder rod in the case of a device thatcorresponds to U.S. Pat. No. 4,958,706 is depicted in FIG. 3, also indotted lines. It is seen that the part of the curve in dotted lines (7)corresponds to the possibilities for adjusting screw (54) and, based onthe adjustment of the screw, point D of the curve in dotted lines moveson horizontal line (8). If it is desired for the shock absorber to have,according to this U.S. patent, operating characteristics that areapproximately normal, movement will take place between the curves thatcome to points D and D′ depending on the adjustment of screw (54). Thebearing that is indicated by the horizontal line in dotted lines (8)corresponds to the maximum pressure that can be tolerated by valve (64)of U.S. Pat. No. 4,958,706. It was deliberately reconsidered that valve(64) be adjusted for the same value as that of point C. It will beeasily understood, however, as was explained above, that point C of thehydraulic brake screw can be adjusted to a higher or lower value. Thus,the shock absorber of the invention offers the advantage of being ableto adapt to forces that are tolerated by the shock absorber according toits use. In fact, when the shock absorber is used on a motorcycle or anautomobile, the maximum compression force at which the hydraulic brakeeffect should be able to be exerted will vary depending on the type ofvehicle.

A first advantage of the invention is therefore to make it possible witha shock absorber of the same type to adapt it both to a motorcycle andto an automobile, as well as to adapt it to road conditions that thevehicle will encounter by moving point C up or down.

Another advantage consists in the fact that for the same givencompression force, which is lower than the maximum acceptable force, theshock absorber, according to the invention, will react with acompression speed and displacement speed of the cylinder rod that aredifferent over a range of speeds that is between point D and point C.These characteristics of different compression speeds contribute to thecomfort of the suspension, i.e., to the adherence of the tire to theground, which makes it possible to impart greater mobility to thevehicle. The compression speed zone that lies between points D′ and C oncurve (8) is in fact compression speeds for which the traditional rubberstop will come into play and in which the vehicle is subjected to thebounce phenomenon that was mentioned at the beginning of thedescription. Likewise, the possibilities for points A and B to beshifted by low-speed (34) and high-speed (35) adjusting screws also makeit possible to better adapt the response curve of the shock absorberaccording to the invention regardless of the type of terrain that isencountered. This is not the case with the invention of U.S. Pat. No.4,958,706; it is possible to choose, by adjusting the screw, to adaptthe response curve in such a way that the latter corresponds to profileD′ so that at low speeds, the vehicle has the response characteristicthat is close to curve (340) of the invention and, in this case, it isseen that at moderate speeds that correspond to curve (350), theresponse of a shock absorber that is adjusted according to the curvethat ends at point D′ will be considerably poorer and the vehicle willreach the elastic stop very quickly. The other possibility is to chooseto make an intermediate adjustment that is depicted by curve (7) thatends at point D and intersects curve (350) at point E. In this case, theresponse of the shock absorber will be a little better for moderatecompression speeds, but the response of the shock absorber will bepoorer at low speeds. Thus, if the path comprises notched sheet metal,the comfort of the vehicle and its mobility will be considerably pooreron the notched sheet metal for a displacement speed that is not veryhigh. In fact, part of curve (340) corresponds to displacements of lowamplitude, whereas part (350, 3640) corresponds to displacements oflarge amplitude for generating the vehicle at the edge of, for example,a pothole.

By manipulating the adjustment of high-speed screw (351) and brakespindle (361), it is thus understood that this makes it possible todefine a shock absorber whose operation will create a hydraulic brake byreplacing elastic stops and whose operation for low speeds will not beaffected by said hydraulic brake characteristic.

Other modifications within the grasp of one skilled in the art will alsobe part of the spirit of the invention.

What is claimed is:
 1. An oil shock absorber system for a vehiclecomprising: a cylinder; a piston in said cylinder for driving oilbetween said piston and a bottom of said cylinder toward a reservoir,said reservoir having a deformable reserve chamber for receiving the oiland a pressurized chamber for deforming the chamber, said reservoirhaving an intermediate chamber and at least three different orificeswherein a flow path for the oil extends through said intermediatechamber and said orifices into said reserve chamber, one of saidorifices being blocked by a first adjustable non-return valveconstituting an adjustable hydraulic brake enabling the oil to evacuatesaid intermediate chamber into the reserve chamber only when pressureexerted by said piston on said oil exceeds a predetermined pressure, anda second adjustable non-return valve blocking a second orifice of saidthree orifices and disposed between said intermediate chamber and saidreserve chamber, said second adjustable non-return valve beingadjustable for a range of piston displacement speeds that lies between afirst low speed and hydraulic brake speeds.
 2. An oil shock absorbersystem according to claim 1 including a third orifice comprising anadjustable constriction enabling the oil to evacuate from theintermediate chamber to the reserve chamber at low speeds.
 3. An oilshock absorber system according to claim 1 wherein the first and secondadjustable non-return valves each comprise a screw element having a rodextending therefrom and over a given height having a notched portionabout a periphery thereof, a holding cap carried by said rod, a sealingwasher and elastic means maintained between said holding cap and saidnotched portion, said elastic means biasing respective sealing washersagainst the seats of orifices associated with respective adjustablenon-return valves.
 4. An oil shock absorber system according to claim 2including a ball engageable with the notched portion and an elasticmeans for biasing the ball into the notched portion.
 5. An oil shockabsorber system according to claim 1 including a cylindrical ring inpart defining said intermediate chamber and having an annular groove,said ring closing an open end of the reserve chamber of the reservoirand said intermediate chamber, said cylindrical ring having holesextending through said ring and said annular groove, said holes beingthreaded for receiving screw elements accessible externally of saidreservoir and seals between said screw elements and said holes.
 6. Anoil shock absorber system according to claim 3 wherein said elasticmeans comprises a stack of Belleville washers mounted at least 2×2opposite one another.
 7. An oil shock absorber system according to claim6 wherein the elastic means for said second non-return valve comprises astack of Belleville washers having a thickness of between 0.20 mm and0.45 mm.
 8. An oil shock absorber system according to claim 6 whereinthe elastic means for said first non-return valve comprises a stack ofBelleville washers with a thickness of between 0.45 mm and 1 mm, theBelleville washers for said first non-return valve having a thicknessgreater than the thickness of the washers of the second non-returnvalve.